Build the Coach snapshot once per turn and widen the round budget to three

Each retrieval tool re-scoped the snapshot to a single source, so its cache key
never matched the inventory's full-source build — a four-tool turn paid four
extra full snapshot builds on top of the inventory's. Thread the inventory's
probe scope to every tool so a per-tool read lands the one cache entry the
inventory already primed, collapsing the turn to a single build (a window
override still gets its own correct build). Raise the loop's round cap from two
to three so a sequential cross-metric why-chain isn't starved; the per-round
token budget is unchanged and the absolute ceiling tracks one above so the
final round still forces prose.

src/app/api/insights/chat/__tests__/route-module-gate.test.ts

@@ -71,9 +71,10 @@ vi.mock("@/lib/ai/coach/types", () => ({
 // thin stub keeps the import graph satisfied without pulling the real schemas.
 vi.mock("@/lib/ai/coach/tools", () => ({
   COACH_TOOL_DEFS: [],
-  MAX_ROUNDS: 2,
+  MAX_ROUNDS: 3,
   buildCoachDataInventory: vi.fn(),
   renderDataInventory: vi.fn(),
+  renderFocusHint: vi.fn(() => ""),
   buildToolModeAddendum: vi.fn(),
   runCoachToolLoop: vi.fn(),
 }));

src/app/api/insights/chat/__tests__/route-tool-mode.test.ts

@@ -138,31 +138,36 @@ vi.mock("@/lib/ai/coach/snapshot", () => ({
 }));
 
 // Tool-module surface — stub the inventory + loop so we assert routing only.
-const { buildCoachDataInventory, renderDataInventory, runCoachToolLoop } =
-  vi.hoisted(() => ({
-    buildCoachDataInventory: vi.fn(async () => ({
-      entries: [],
-      restMode: false,
-      cycleEnabled: false,
-      window: "last30days",
-    })),
-    renderDataInventory: vi.fn(
-      () => "DATA INVENTORY\n- blood pressure: present",
-    ),
-    runCoachToolLoop: vi.fn(async () => ({
-      result: { content: "Your BP is steady.", tokensUsed: 80, model: "m" },
-      workingProviderType: "anthropic",
-      totalTokens: 80,
-      rounds: 2,
-      toolTrace: [{ name: "get_metric_series", present: true }],
-      toolResults: [],
-    })),
-  }));
-vi.mock("@/lib/ai/coach/tools", () => ({
-  COACH_TOOL_DEFS: [{ name: "get_metric_series" }],
-  MAX_ROUNDS: 2,
+const {
   buildCoachDataInventory,
   renderDataInventory,
+  renderFocusHint,
+  runCoachToolLoop,
+} = vi.hoisted(() => ({
+  buildCoachDataInventory: vi.fn(async () => ({
+    entries: [],
+    restMode: false,
+    cycleEnabled: false,
+    window: "last30days",
+    probeScope: { sources: ["bp", "hrv"], window: "last30days" },
+  })),
+  renderDataInventory: vi.fn(() => "DATA INVENTORY\n- blood pressure: present"),
+  renderFocusHint: vi.fn(() => ""),
+  runCoachToolLoop: vi.fn(async () => ({
+    result: { content: "Your BP is steady.", tokensUsed: 80, model: "m" },
+    workingProviderType: "anthropic",
+    totalTokens: 80,
+    rounds: 2,
+    toolTrace: [{ name: "get_metric_series", present: true }],
+    toolResults: [],
+  })),
+}));
+vi.mock("@/lib/ai/coach/tools", () => ({
+  COACH_TOOL_DEFS: [{ name: "get_metric_series" }],
+  MAX_ROUNDS: 3,
+  buildCoachDataInventory,
+  renderDataInventory,
+  renderFocusHint,
   buildToolModeAddendum: vi.fn(() => "TOOL ADDENDUM"),
   runCoachToolLoop,
 }));
@@ -246,11 +251,11 @@ describe("coach chat — tool-mode routing (F1)", () => {
       { providerType: "anthropic", instance: {} },
     ]);
     await post(chatReq({ message: "How is my BP?" }));
-    // maxTokens (1500) × MAX_ROUNDS (2). The 4th arg is the provider-aware
+    // maxTokens (1500) × MAX_ROUNDS (3). The 4th arg is the provider-aware
     // daily cap (F1) — mocked to the user-plan ceiling for this BYOK chain.
     expect(reserveBudget).toHaveBeenCalledWith(
       "u1",
-      3000,
+      4500,
       "2026-06-21",
       2_000_000,
     );

src/app/api/insights/chat/route.ts

@@ -575,6 +575,11 @@ Reply now as the assistant, in ${locale === "de" ? "German" : "English"}. Fetch
         temperature: AI_BUDGETS.coach.temperature,
         maxTokens: AI_BUDGETS.coach.maxTokens,
         fallbackWindow: effectiveScope?.window,
+        // v1.21.0 (D5-1) — share the inventory's full-source snapshot across
+        // every tool so the turn builds ONE snapshot, not one per tool. The
+        // probe scope is the exact scope the inventory was built against, so the
+        // per-tool reads land its 60s LRU entry.
+        sharedScope: inventory.probeScope,
         // v1.20.1 — thread the abort signal so a mid-generation disconnect tears
         // down the per-round provider calls instead of paying the full cost.
         signal: request.signal,